This invention relates generally to apparatus for controlling superheated vapor temperature by direct contact desuperheating and more particularly to upright type attemperators which spray a cooling liquid into the vapor stream.
The known attemperators of the type under consideration have encountered difficulties in achieving complete vaporization of the liquid spray within the attemperator during conditions of low spray input. These difficulties arise from the fact that atomization of the liquid is less than optimum at low flows causing the spray being injected in the vapor stream to include relatively large drops of liquid which often do not reach saturation temperature before leaving the attemperator. Efforts to overcome these difficulties have included provisions for draining accumulated liquid from the attemperator containment vessel and for increasing the pressure drop across the attemperator so as to induce flashing of the liquid. Both of these approaches have undesirable effects, the former results in heat loss whereas the latter creates excessive pressure drop at high load.
The prior art is exemplified by German Pat. No. 1,012,308 which discloses an upright type attemperator whose containment vessel includes a sleeve concentric with the vessel and spaced therefrom to form an annular passageway therebetween. During operation of this referenced attemperator, the liquid drops which do not reach saturation are collected in the annular passageway and drained therefrom with concomitant heat loss.